About the Shutter Speed for Motion Calculator
This shutter speed calculator tells you how fast your shutter needs to be to freeze a moving subject. Enter how fast the subject moves, how far away it is, your focal length, sensor size and resolution, and the amount of blur you are willing to accept in pixels. The calculator works out how quickly the subject’s image sweeps across the sensor and returns the slowest marked shutter speed that keeps the streak within your limit, plus the blur you would get at any shutter speed you type in.
It is useful for sports, wildlife, motorsport, kids and pets, and street photography — anywhere you need to decide between a crisp frame and the lowest possible ISO. Because blur depends on the image moving across the sensor rather than on the subject alone, a long lens or a close subject needs a much faster shutter than the same subject shot wide or from far away.
The result assumes a steady camera (tripod, fast stabiliser or a panning-free hand-held shot) and constant subject speed. Movement straight toward or away from the camera blurs far less than motion across the frame, so pick the angle that matches your scene. Real subjects often have faster-moving parts — legs, wings, wheels — so treat the answer as a minimum.
How to use the shutter speed for motion calculator
- 1Enter how fast the subject is moving and pick the unit.
- 2Enter the distance to the subject and your actual focal length.
- 3Choose your sensor size and enter the image width in pixels.
- 4Set how many pixels of blur you can accept and the direction of motion.
- 5Read the recommended shutter speed, then type your own speed in “Check a shutter speed” to see its blur.
Formula and method
The subject’s image moves across the sensor at its own speed multiplied by the optical magnification. For a lens focused at distance d, thin-lens magnification is m = f ÷ (d − f), which is close to f ÷ d for anything more than a few focal lengths away. Only the part of the motion that crosses the frame matters, so the speed is multiplied by the sine of the angle between the direction of travel and your line of sight.
Converting millimetres per second on the sensor into pixels per second (image width in pixels ÷ sensor width in mm) gives the blur rate. Dividing your acceptable blur in pixels by that rate gives the longest exposure that still freezes the subject. The recommended setting is the slowest standard third-stop shutter speed that is at least that fast.
- v
- Subject speed (m/s)
- θ
- Angle between direction of motion and line of sight (90° = across the frame)
- f
- Focal length (m)
- d
- Distance from camera to subject (m)
- s
- Image speed on the sensor (px/s)
- B
- Acceptable blur (px)
- t_max
- Longest exposure that keeps blur within B (s)
Worked examples
Car at 50 km/h, 30 m away, 100 mm on full frame
At 30 m a 100 mm lens magnifies by 0.1 ÷ 29.9 ≈ 0.00334, so a 13.9 m/s car moves 46.5 mm/s across a 36 mm sensor — about 7,742 px/s on a 6000-px image. Keeping blur to 2 px needs 2 ÷ 7,742 ≈ 1/3871 s, so the nearest marked speed is 1/4000 s. At 1/1000 s you would see about 7.7 px of blur.
Bird in flight at 40 km/h, 40 m away, 300 mm on APS-C
A 300 mm lens at 40 m magnifies by 0.3 ÷ 39.7 ≈ 0.00756. An 11.1 m/s bird therefore crosses the 23.5 mm sensor at about 84 mm/s, or roughly 21,437 px/s on a 6000-px image. Allowing 4 px of blur needs about 1/5359 s, so the slowest marked speed that works is 1/6400 s; 1/2000 s would smear the bird by about 10.7 px.
Kids running diagonally at 12 mph, 20 ft away, 50 mm
12 mph is 5.36 m/s, and at 45° only 70.7% of that crosses the frame. At 6.1 m a 50 mm lens gives 31.4 mm/s on the sensor, about 5,228 px/s. Holding blur to 3 px needs 1/1743 s, so set 1/2000 s — the common 1/250 s would leave about 21 px of blur.
Frequently asked questions
What shutter speed freezes motion?+
It depends on how fast the image moves across the sensor, not just the subject. As rough starting points, walking people need about 1/250 s, running kids and pets 1/1000 s, field sports 1/1000–1/2000 s, and birds in flight or motorsport with a long lens 1/2000–1/4000 s or faster.
Why does a longer lens need a faster shutter speed?+
Doubling the focal length doubles the magnification, so the subject’s image moves twice as fast across the sensor and blurs twice as much in the same exposure. Moving twice as close has the same effect, which is why tight framing demands faster speeds.
Does a higher-megapixel camera need a faster shutter?+
If you judge sharpness at 100% view, yes — more pixels across the same sensor width means the image crosses more pixels per second. If you only view the whole image at a fixed print or screen size, the visible blur is the same, so you can allow proportionally more pixels of blur.
Does image stabilisation help freeze a moving subject?+
No. Stabilisation counteracts camera shake, not subject movement. It lets you hand-hold slower speeds for static scenes, but a moving subject will still blur if the shutter is too slow. Only a faster shutter, flash or panning reduces subject motion blur.
How much motion blur is acceptable?+
One to two pixels is effectively invisible when pixel-peeping. Three to five pixels is usually invisible in a full-screen view or a typical print, and images downsized for social media can tolerate ten or more pixels of blur in the original file.